Recently, development of a low fuel cost type automobiles has been demanded for promoting energy savings, and therefore an electric automobile driven by a motor, and a hybrid automobile running by a combination of motor driving and engine driving have been attracting attention. According to these types of vehicles, a large-capacity motor mounted thereon is difficult to drive and control by direct current voltage supplied from a battery, wherefore a power converter operable by switching of power semiconductors is an essential device for achieving voltage boosting and alternating current control. Moreover, it is important that the power semiconductors which generate heat when energized have a cooling structure for cooling the power semiconductors.
According to a semiconductor device disclosed in PTL 1, a pair of heat sink electrodes are provided in such positions that a semiconductor element is sandwiched between the heat sink electrodes, and the heat sink electrodes thus positioned are sealed by mold resin. The semiconductor element can be efficiently cooled when the heat sinks functioning as electrodes as well are attached to a cooling surface of a cooling unit, for example. According to this structure, an insulation sheet having high heat conductivity or the like is disposed between the cooling surface and each of the heat sink electrodes so as to secure electric insulation.